中海淡水化過程における塩分拡散機構(第2報) : 湖底摩擦係数の推定

抄録・要旨

One of the nlost important problems in the hydraulic model test to investigate lake current variation is how to assume the value of the bottom friction coeficient defilned by C_f=τ_b/ρU^2_b in which τb is shearing stress acorss the bottom, ρ density of fluid and U_b bottom velocity of flow. Several methods to estimate C_f, wave spectrum method, significant wave method were proposed, but for the lack of data it is impossible to apply the methods mentioned to the case of Nakaumi Sea. In this paper, from shearing stress caused by wind on the water surface and hydraulic gradient observed on Shinji Lake, the value of C_f is quantatively estimated on the assumption that the hydraulic pecurialities of Shinji Lake can be regarded as similar to that of Nakaumi Sea for the limited purpose of the investigation of the lake current variation. The values of C_f obtained ranges from 2 × <10>^<-3> to 24 × <10>^<-3> (C.G.S) and the mean value of C_f is nearly 7 × <10>^<-3> (C.G.S). It should be noticed that these values of C_f are nearly equal to the values generally expected and no correlation between C_f and wind velocity W is recognized so far as the results obtained up to the present are considered. Some suggestions to the future studies are given by the author's trial calculations.